Telephone and like multi-wire distribution systems of several types are in widespread use and a wide variety of modules and connectors are known and used for replacement or add-on splicing in such systems. One such type in extensive use is disclosed in Frey et al U.S. Pat. No. 3,772,635, issued Nov. 13, 1973, and assigned to Bell Laboratories Incorporated, Murray Hill, N.J., in which a basic splice unit (hereinafter typically referred to as a Bell.RTM. type two-wire butt assembly and shown herein at FIG. 11A) is made up in the field of three parts, an index strip, a connector module, and a cap, with one multi-wire group being installed between the index strip and connector module and another multi-wire group to be joined thereto being installed between the connector module and the cap. As also shown and discussed in said U.S. Pat. No. 3,772,635 and in FIG. 11A hereof, the Bell.RTM. type two-wire butt assembly made up of these parts may have connected thereto an additional multi-wire group terminating in a so-called bridging module (hereinafter typically referred to as a Bell.RTM. type bridging module). However, because of the nature of the construction of the Bell.RTM. type two-wire butt assembly and Bell.RTM. type bridging module, only one bridging module can be added to any given two-wire butt assembly and, if a given installation requirement dictates yet another multi-wire group be added to the assembly or be substituted for one of the wire groups interconnected in the butt assembly, the butt assembly must be destructed in the sense of disconnection of the wire groups from the assembly, which is a time-consuming and costly field effort.
Stackable or pluggable multi-wire modules or connector systems are also known and extensively used in the art, such as disclosed in Enright U.S. Pat. No. 3,708,779, issued Jan. 2. 1973, and assigned to Minnesota Mining and Manufacturing Company (and known in the art as the 3M.RTM. multi-wire system) and in Fleishhacker U.S. Pat. No. 4,162,815, issued July 31, 1979, and assigned to AMP.RTM. Incorporated (and known in the art as the AMP.RTM. type distribution system). Connector components of these other systems (the 3M.RTM. system and the AMP.RTM. system) are incompatible with each other and with the Bell.RTM. type distribution system and its splicing assemblies and connector modules, and are further limited in their ability to plug and unplug any given wire group, i.e. in many instances a changeover from one distribution arrangement to another distribution arrangement must necessarily involve disconnection of service of certain groups in order to make the reconnection or resplice. This is because the so-called stackable or pluggable multi-wire splicing modules or connectors disclosed in said U.S. Pat. Nos. 3,708,779 and 4,162,815 are of two-sided construction, with the consequence that any intermediate module or connector in a stack cannot be easily accessed except by disconnection from at least one adjacent module or connector before reconnection to another. Moreover, from the point of view of those involved in the task of field splicing in these systems, the 3M.RTM. and AMP.RTM. plug type modules or connectors are as a practical matter considerably more cumbersome to build in the field and to use than is the Bell.RTM. type bridging module.
It is a further disadvantage, from the point of view of field splicing operations, that all of these prior splicing systems, the Bell.RTM. type, the 3M.RTM. type, and the AMP.RTM. type, involve the construction or "building" of the splicing module or connector in the field, with but one person working on one splice at a time, which limits the productivity of a splicing crew. This is because the splice usually must be "built" within the confines of a so-called splice case. In contrast, and as more specifically discussed hereinafter, the distribution module of the present invention, which does not involve the installation of the individual wires of the multi-wire group in the distribution module itself in the field, avoids this limitation on splicing crew productivity.
As earlier indicated in general terms, the Bell.RTM. type two-wire butt assembly offers very little flexibility for adding on or substituting an additional wire group, since its wire groups cannot be "unplugged" except by physical destruction of the assembly. Field practice in this respect involves cutting of the wires from the assembly and discarding the module, with the whole section of wire cable sometimes also being abandoned and replaced by another because there is not sufficient wire length left to install the original wire in another module.
It is also a disadvantage of the AMP.RTM. type and 3M.RTM. type distribution system splicing components that the splicing apparatus is inherently relatively complex and relatively difficult to handle in the field, particularly with respect to wire continuity testing. Incorporation of distribution modules according to the present invention, with wire group connections on three or more sides, renders continuity testing relatively simple, which can substantially improve field crew productivity even aside from the relatively simple splicing module construction involved, i.e. bridging modules such as the Bell type bridging module with prong type individual wire connectors are relatively easy to field construct and test.
Use of distribution modules and associated extender connectors according to the present invention is entirely compatible with the splicing components utilized in the Bell.RTM. multi-wire distribution splicing systems such as disclosed in U.S. Pat. No. 3,772,635, with which the two-sided pluggable modules used in the AMP.RTM. and 3M.RTM. type splicing systems are not compatible. Moreover, methods of the present invention overcome major disadvantages of the Bell type splicing system, wherein add-on is limited to one additional wire group bridging module, and wherein wire group substitution in the two-wire butt assembly can be done only by destruction of the assembly. By use of the present invention, the Bell.RTM. type splicing system, and other splicing systems as well, are rendered completely pluggable and completely flexible from the point of view of changing the distribution system without component destruction and without circuit interruption.